全新java初学者实践教程6(Java SE5.0版)
~AbTbQ3 基本语法3
}Gg:y? E{B=%ZNnm ohj(1jt 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
STY\c5 -cW'g [font="Times] 1.循环语句[font="Times]:while,do-while,for
&S|%>C{P.w i%eq!q [font="Times]2.分支语句[font="Times]:if-else,switch,
t;e+WZkV [font="Times]
l!^+Xeg~ 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
iF1E 5{dH [font="Times]
5<?s86GHh' 4.异常处理语句[font="Times]:try-catch-finally,throw
B>"O~ gZ{# fKN&0N|^R 实践:
~Dz`O"X3 [font="Times] 1.循环语句
F1aI4H<(T [font="Times] while 语句
b9gezXAcd [font="Times]class While {
,Kw]V %xOb [font="Times]public static void main(String args[]) {
6I`Lszs [font="Times]int n = 10;
mFdj+ &2\ [font="Times]while(n > 0) {
3
2MdDa [font="Times]System.out.println("tick " + n);
w;Jby [font="Times]n--;
,
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}g\1JSJ%H [font="Times]}
ohPCYt [font="Times]}
;mw$(ZKa# [font="Times] do…while 语句
p2Fff4nQ [font="Times] class DoWhile {
vOl<
[font="Times]public static void main(String args[]) {
@CJ`T& [font="Times]int n = 10;
4$^\s5 K [font="Times]do {
6*]g~)7`Q~ [font="Times]System.out.println("tick " + n);
>|S&@< [font="Times]n--;
d|RqS`h
] [font="Times]} while(n > 0);
1!4-M$- [font="Times]}
Xi~%,~ [font="Times]}
_'"whZ)2 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
^OWA [font="Times] for语句
NEb M>1>^ [font="Times] class ForTick {
;I^+u0ga [font="Times]public static void main(String args[]) {
l9eCsVQ~V [font="Times]int n;
iE;D_m.>`O [font="Times]for(n=10; n>0; n--)
d}2$J1` [font="Times]System.out.println("tick " + n);
L~u@n24 [font="Times]}
" A}S92 [font="Times]}
X?8 EPCk 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
R
rtr\a 还有啊,[font="Times]for循环的部分可以为空的
qP}187Q1 [font="Times]class ForVar {
sD!)= t_ [font="Times]public static void main(String args[]) {
7|/Ct;oO: [font="Times]int i;
vTdJe [font="Times]boolean done = false;
g$N/pg2>cT [font="Times]i = 0;
8wXnc% [font="Times]for( ; !done; ) {
[7btoo|P] [font="Times]System.out.println("i is " + i);
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{>hG4 [font="Times]if(i == 10) done = true;
>-0\wP [font="Times]i++;
_,?<r&>v6 [font="Times]}
7l~d_<h [font="Times]}
qZS]eQW. [font="Times]}
循环语句的例子下载 FZ0wtS2 [font="Times] 2.分支语句[font="Times]
fUg<+|v* [font="Times] if/else语句
;;zQV D )X [font="Times]class IfElse {
Sl!#!FGI [font="Times]public static void main(String args[]) {
nN]GO} [font="Times]int month = 4; // April
~mR@L `"l [font="Times]String season;
26&$vgO~: [font="Times]if(month == 12 || month == 1 || month == 2)
-*<4 hFb [font="Times]season = "Winter";
|g@n'^] [font="Times]else if(month == 3 || month == 4 || month == 5)
U_8 Z& [font="Times]season = "Spring";
6Kbc:wlR [font="Times]else if(month == 6 || month == 7 || month == 8)
$Sx(vq6( [font="Times]season = "Summer";
>OLKaghV.5 [font="Times]else if(month == 9 || month == 10 || month == 11)
{#_CzI.0f [font="Times]season = "Autumn";
e` QniTkT [font="Times]else
hT0[O [font="Times]season = "Bogus Month";
sgGXj7 [font="Times]System.out.println("April is in the " + season + ".");
S#^2k!(|G [font="Times]}
z[0+9=<Y [font="Times]}
>]!8f?, [font="Times]//这段程序输出[font="Times]:
)9]DJ!]&Q" [font="Times]//April is in the Spring.
wOLDHg_ [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
QH d^?H* [font="Times] switch语句
;K$ !c5 [font="Times] class Switch {
?^Q8#Y^M [font="Times]public static void main(String args[]) {
:]rb} 1nLB [font="Times]int month = 4;
l+vD`aJ 3 [font="Times]String season;
){I0 [font="Times]switch (month) {
!2o1c [font="Times]case 12:
@CTSvTt$ [font="Times]case 1:
)-s9CWJv [font="Times]case 2:
cEK<CV [font="Times]season = "Winter";
IrMUw$ [font="Times]break;
..K@'*u [font="Times]case 3:
F4*ssx [font="Times]case 4:
9zL(PkC%\ [font="Times]case 5:
vmj'X>Q [font="Times]season = "Spring";
L7`=ec< [font="Times]break;
]J(BaX4 [font="Times]case 6:
^cnTZzT#Q [font="Times]case 7:
J85S'cwZZ [font="Times]case 8:
l"rX'g? [font="Times]season = "Summer";
+L,V_z [font="Times]break;
#
E{2 !Z [font="Times]case 9:
]i:_^z)R [font="Times]case 10:
\V_Tc` [font="Times]case 11:
(k^o[H F [font="Times]season = "Autumn";
_m.w5nJ [font="Times]break;
Iysp) [font="Times]default:
qN"Q3mU^h* [font="Times]season = "Bogus Month";
qI%X/' [font="Times]}
9Rm\@E
[ [font="Times]System.out.println("April is in the " + season + ".");
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a_3w/9L4r [font="Times]}
分支语句代码下载 :Dj0W8V j>`-BN_ [font="Times]switch语句适合于条件非常多的逻辑
4Jf9N' 请看上述语句可以混合使用,请看
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